When doing a kickstart install of 6.1, using

  network --bootproto dhcp
  nfs --server 192.168.1.100 --dir /install/redhat/rh61-cdrom

and DHCP server configured with

  server-identifier 192.168.1.100;
  deny unknown-clients;

  subnet 192.168.1.0 netmask 255.255.255.0 {
        option routers 192.168.1.1;
        option domain-name-servers 192.168.1.100;
 }

  host host_101 {
    hardware ethernet xx:xx:xx:xx:xx:xx;
    fixed-address 192.168.1.101;
    next-server 192.168.1.100;
    filename "/install/conf/kickstart/probe.cfg";
 }

the computer being installed fails to reverse map its IP address,
asking questions about 101.1.168.192.in-addr.arpa.localdomain
instead of just 101.1.168.192.in-addr.arpa.

To be able to install I have to add an extra zone to my nameserver,
for the bogus in-addr.arpa.localdomain domain.